Heating apparatus comprising combustible gas burner

ABSTRACT

A combustible gas heating apparatus includes:
         a main burner arranged in a combustion chamber of the apparatus,   a pilot burner for generating a pilot flame for igniting it,   a valve group comprising a main valve arranged on a main duct, and a pilot valve arranged thereon, upstream of the main valve, for supplying gas to the pilot burner,   a system for controlling gas to the main and pilot burners, including an electronic control unit operatively associated with the main and pilot valves,   a thermal safety device actuable in the presence of inflammable vapors near the apparatus, to safely extinguish the main burner when a predetermined temperature threshold has been exceeded,   the pilot burner configured as a continuous pilot burner having a permanent flame,   the pilot and main valves being electrically-operated valves,   an auxiliary buffer battery configured to power the electronic control.

TECHNICAL FIELD

The present invention relates to a heating apparatus comprising acombustible gas burner.

TECHNOLOGICAL BACKGROUND

The invention is applicable in particular, although not exclusively, tothe technical field of water heating apparatuses, that is sanitary waterheaters or heaters for water circulating in plants for heatingenvironments.

More specifically, combustible gas apparatuses in which the invention isused typically comprise a pilot burner for generating a pilot flame, anda main burner for generating a main flame, in which combustion isinitiated in the main burner by means of the pilot flame.

A first type of apparatuses of this kind provides the use of acontinuous pilot burner, that is having a permanent flame, in which thepilot flame remains ignited from the moment the apparatus is switchedon, provided it is not switched off.

Apparatuses of this type are generally not connected to the mains. Inthese apparatuses, a magnetic safety group is associated with the pilotvalve that comprises a thermocouple (or thermopile) and as a systemconnected thereto having a manual cocking feature, and at least one mainvalve having a mechanical or electrical operator (preferably powered bythe energy produced by the thermopile) for directly or indirectly(servo-assisted system) commanding a gas circuit to a main burner. Athermostat that compares the temperature of the water set by the userwith the actual temperature detected by the sensor manages the ignitionof the main burner on the basis of the amount of heat required.

In compliance with specific applicable regulations, thermal safetydevices also need to be used in these apparatuses, which devices aredesigned to intervene when inflammable vapours are present in thevicinity of the heating apparatus. In this type of apparatuses, thethermal safety devices, also known in the field by the abbreviation TCO(“Thermal Cut Off”), are designed as mechanical devices. These aresimilar to thermal interrupters, which are suitable for monitoring thetemperature inside the combustion chamber. The ignition of inflammablevapours inside the combustion chamber causes the temperature in saidchamber to rise, thereby causing the TCO device to intervene when apredetermined threshold temperature is exceeded. The TCO device can be a“single-use” TCO (for example by using a thermally fusible element) or aresettable TCO.

In continuous pilot heating apparatuses, the known types of such TCOsafety devices can work in series with the flow of air that enables thecombustion such that, by intercepting said flow of air by means ofappropriate interception components that are activated by the TCOdevice, the main burner and the pilot burner are in fact extinguished.Alternatively, these devices can work in series with the thermocouple,thereby causing the pilot flame and consequently also the main burner tobe extinguished (intercepting the passage of gas).

Continuous pilot heating apparatuses equipped with the TCO safetydevices mentioned above are advantageous in that these TCO devices arerobust and inexpensive. Furthermore, if a small amount of inflammablevapours is present, said vapours are burnt by said pilot flame, which isalways ignited even during the standby periods of the apparatus, therebyreducing the risk of explosion. In contrast, that is with a largeramount of vapours, the TCO safety devices intervene.

Such apparatuses are not affected by the drawbacks connected with themains either, since they are not connected thereto and the fact that thepilot flame is always ignited guarantees ease of ignition.

In contrast, this type of continuous pilot apparatuses are marked bymanual ignition of the pilot burner which is impractical and not easyfor the user to use (requiring the user to press the button on thecocking group for a certain amount of time, simultaneously actuating theigniter, and then to release the button as soon as the thermocoupleactivated by the flame has energised the magnetic group of the pilotvalve).

Another limitation of such apparatuses is connected to the fact that,during the periods of rest (standby) of the main burner, the pilot flamedissipates all the energy it produces. The thermoelectric generator(thermocouple/thermopile) is likewise subjected to ageing and loss ofperformance, thereby generating less current over time than what isneeded to activate the magnetic group.

A second type of such heating apparatuses provides the use of anintermittent pilot burner, that is in which the pilot flame is onlyignited after heat has been requested, this causing the ignition of themain burner. These apparatuses typically need to be connected to themains and are provided with a circuit board that forms the electroniccontrol unit of the pilot valve and of the main valve, said valvestherefore both being designed as electrically operated valves (electricvalves).

The intermittent pilot burner is provided with an igniter electrode anda sensor for electronically controlling the flame (for example a flameionisation sensor) as well as a thermostat for igniting andextinguishing the pilot burner and the main burner.

In order to fulfil the function of protection against the ignition ofinflammable vapours, electronic sensors, also known in the field by theabbreviation “FVI” (Flammable Vapor Sensor) are normally used in thissecond type of apparatuses. These electronic sensors are positionedoutside the combustion chamber and are provided with an electricalresistance that is dependent on the concentration of inflammablevapours. The circuit board is designed to monitor the value of theresistance of the sensor in order to prevent the apparatus fromswitching on if a high concentration of inflammable vapours is detected.

This type of apparatus has the advantage of providing automatic ignitionand is also more energy efficient since the pilot only remains ignitedfor the time required to ignite the main burner and until the mainburner has been ignited, but, if the main burner is extinguished(standby), the pilot burner is also extinguished. It is alsoadvantageous on account of having automatic reignition if the pilotflame is accidentally extinguished (for example in the event of a gustof wind, a temporary absence of gas, etc.).

In contrast, since these apparatuses require a mains power supply, theycannot function in the event of a blackout (thereby not guaranteeingthat the user has hot water for the entire duration of the black-out).Furthermore, the FVI electronic sensors are expensive and not veryrobust insofar as they suffer from the so-called phenomenon of “nuisanceshut off” or “false positives”, meaning they also intervene in theabsence of inflammable vapours because they are sensitive tocontaminants. Another limitation is that the inflammable vapours are notburnt by the pilot flame, which in fact only remains ignited for thetime required to ignite the main burner, and is then extinguished.

There may also be external conditions (for example low temperatures,contaminants and moisture on the ignition electrode or the detection ofa flame, etc) that make ignition difficult.

DESCRIPTION OF THE INVENTION

One main principle that forms the basis of the present invention is thatof providing a heating apparatus, which comprises a combustible gasburner and the structure and function of which are designed to overcomethe limitations indicated above with reference to the known solutions.

These and other objects that will clearly appear in the following areachieved by the invention by means of a heating apparatus comprising acombustible gas burner, which is formed in accordance with the attachedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will become clearerfrom the following detailed description of a preferred embodimentthereof, which is illustrated by way of non-limiting example, withreference to the only attached FIGURE, which is a schematic view of themain parts of a heating apparatus formed in accordance with theinvention.

PREFERRED EMBODIMENTS OF THE INVENTION

With reference to the cited FIGURE, 1 denotes an example of a heatingapparatus as a whole, comprising a gas burner, which is only depictedschematically and is formed in accordance with the present invention.

Said apparatus can be designed as a sanitary water heater or a heaterfor water intended to be circulated in a plant for heating environments.

The apparatus 1 comprises a main burner 2 arranged in a combustionchamber 3, on which burner a main flame is generated, a pilot burner 4,which is suitable for generating a pilot flame in order to ignite themain burner 2, and a valve group 5.

The valve group 5 comprises a main valve 6, which is arranged on a mainduct 7 of the valve group, for supplying the combustible gas to the mainburner 2, and a pilot valve 8, which is arranged on the duct 7 upstreamof the main valve, for supplying the gas to the pilot burner. 9 denotesa pilot duct, which branches off from a portion 7 a of the main duct 7that is situated between the pilot valve 8 and the main valve 6 and issuitable for feeding the gas to the pilot burner 4.

The main valve 6 and the pilot valve 8 are suitably formed aselectrically operated valves, that is electric valves provided withrespective actuators that are active on the corresponding shutters ofthe valves, which actuators are energised by supply signals that arecarried through respective electrical supply circuits 6 a, 8 a. In theFIGURE, circuits 6 a, 8 a and other electrical connection paths to andfrom the circuit board are depicted by a dot-dashed line.

The supply signals originate from an electronic control unit 10, whichis formed as a circuit board and is operatively associated with saidvalves in order to enable the passage of gas through the correspondingvalve seats. Said control unit is part of a control system of theapparatus, which is designed to control the supply of gas to the pilotand main burners.

The control unit 10 is supplied with power by means of a connection tothe mains, marked as 11, which is suitable for supplying an alternatingvoltage having a preset frequency, for example.

12 denotes a thermal safety device as a whole, which can be activatedwhen inflammable vapours are present in the vicinity of the apparatus,said device being designed to activate the safe switch-off of the mainburner 2 and the pilot burner 4 when a predetermined thresholdtemperature is exceeded in the combustion chamber.

In one embodiment, the thermal safety device 12 comprises aninterception component 13 that is intended for selectively interceptingthe flow of air entering the combustion chamber 3 and is suitable forigniting the flame of the main burner. The interception component 13acts on an opening 13 a, through which the flow of air enters thecombustion chamber, and can be activated, for example, by the fusion ofa fusible element (not shown) that acts as means for stopping theoperating stroke of the interception component, said component beingsubjected to resilient preload, for example.

If the threshold temperature mentioned above is exceeded, the stop meansfuses, thereby enabling the closing stroke of the interceptioncomponent.

13 b denotes a duct for evacuating fumes from the combustion chamber,which, in order for efficient heat exchange, is designed to extendinside a tank 13 c for water intended to be heated by means of theheating apparatus.

13 d marks a temperature sensor (arranged in the tank for detecting thetemperature of the water) of an electronic water thermostat, whichsensor is operatively associated with the control unit 10 and isdesigned to compare the temperature of the water set by the user withthe actual temperature detected by the sensor.

In one embodiment, the thermal safety device 12 can comprise amechanical thermostat, marked as 14 in the FIGURE, which is arranged ina suitable position in the combustion chamber and is operativelyconnected to the control unit 10. The thermostat 14 can change state ifthe temperature in the combustion chamber exceeds the preset thresholdtemperature, and the control unit is designed to identify that thethermostat 14 has changed state, intervening with a command to safelyextinguish the main burner as a result.

For ease of representation, both the embodiments of the thermal safetydevice 12, that is comprising the interception component 13 and thethermostat 14, respectively, are shown in the diagram in the attachedFIGURE, these, however, being considered to be alternative solutions toone another, and are therefore individually applied to the apparatus inalternative ways.

The apparatus 1 likewise comprises a device for damping down flames,denoted by 15 and represented only schematically in the FIGURE, which isintended for blocking the propagation of the flame outside theapparatus. In one embodiment, the device 15 comprises a fireproof gridcomprising holes that runs around the outside of the combustion chamber.The mesh arrangement of said grid is intended to prevent flames fromescaping into the environment when inflammable vapours that are burnt bythe flames of the burners of the apparatus are present.

16 marks a flame-detection electrode, which is arranged near to thepilot flame and is operatively connected to the control unit 10.

17 marks a discharge electrode/flame ignition electrode, which is alsoarranged near to the pilot burner and is operatively connected to thecontrol unit.

In one embodiment, the functionalities of the electrodes 16 and 17 canbe integrated in a single electrode.

In accordance with one aspect of the invention, the pilot burner 4 issuitably designed as a continuous pilot burner, that is having apermanent flame, and, in a preferred embodiment, the pilot valve 8 isdesigned to be supplied with power by means of the control unit 10, froman auxiliary buffer battery 18, which can order the correspondingactuator of the pilot valve to open said pilot valve so as to ensurethat the flame of the pilot burner is maintained in the event of a mainsblackout, that is in the temporary absence of a power supply from themains to the pilot valve.

In other words, the buffer battery 18 is intended for supplying power tothe control unit 10 in the temporary absence of a mains power supply,such that the control unit in turn orders the pilot valve to open/closeduring the temporary absence of a mains power supply.

In one embodiment of the invention, the buffer battery 18 is designed toalso supply power to the main valve 6, in addition to the pilot valve,by means of the control unit so as to ensure the functionality of theapparatus during a temporary absence of a mains power supply.

With particular reference to the electronic unit 10 for controlling theapparatus, said unit is operatively associated with an ON button,denoted by 19, by means of which the unit is activated, therebyinitiating the procedure of igniting the pilot burner, and an OFFbutton, denoted by 20, by means of which the user can interrupt thesupply of power to the control unit 10, consequently commanding thepilot and main valves to close. 21 marks a dial for regulating thetemperature, which is only depicted schematically and by means of whichthe user can select the desired temperature. The dial for regulating thetemperature can alternatively function by means of two or more buttonsfor selecting the temperature and by a series of LEDs or by an LCDscreen.

During operation, the ignition procedure is therefore easy for the userto activate. In fact, starting from a non-operative state of theapparatus, by pressing the ON button, the user activates the circuitboard of the control unit and initiates the ignition process.

Said process provides that the pilot valve 8 (which enables the passageof gas through the pilot burner 4) is opened and provides ignitiondischarge by means of the igniter electrode 17. Once the pilot flame hasbeen ignited, the control unit 10 is notified that the pilot flame hasbeen ignited by means of the flame sensor 16 (electrode for detectingthe flame, which operates by detecting the ionisation current forexample).

The pilot burner 4 can be ignited following a prolonged OFF period (theuser completely turns off the application by means of the OFF button),or following the loss of the pilot flame during operation (for examplethe loss of the flame caused by gusts of wind, by a temporary absence ofgas, by a blackout, or following the intervention of the thermal safetydevice).

In the event of prolonged OFF periods, the user needs to be present inorder to switch on the control board 10 by means of the ON button. It isessential for the user to be present, since otherwise, after longperiods of inactivity in which the application is switched off,inflammable vapours may have accumulated that the thermal safety device12 would not be able to detect.

The user therefore oversees whether or not inflammable vapours arepresent.

The circuit board of the control unit 10 keeps the pilot flame ignitedeven when no heat is requested (this being the continuous pilot burner).

This characteristic allows for the thermal safety device 12 to functioncorrectly, which, as a mechanical thermal safety device, only functionsif at least the pilot burner 4 remains ignited (so as to burn theinflammable vapours that may have accumulated and by the thermal safetydevice 12 intervening if the predetermined threshold temperature isexceeded).

In the event that the mains lacks electric current, for example as aresult of a temporary blackout, advantage is taken of the buffer battery18 that maintains the supply of power to the pilot valve (and possiblythe main valve) by means of the circuit board. In the absence of abuffer battery, the circuit board of the control unit would bedeenergised and therefore the valves 6 and 8 would close and the pilotand main flames would be extinguished; in the event of an accumulationof inflammable vapours during the period in which there is no electriccurrent, the function of the thermal safety device 12 would not beperformed because this device cannot operate when the pilot burner isextinguished. As a result, the subsequent ignition in order to restorethe electric current in the mains would result in dangerous situations.

Furthermore, without the provision of the buffer battery 18, the userwould have to switch the apparatus back on by hand in the event of apower failure.

The situation in which the pilot flame is extinguished as a result ofbrief periods of no gas, due to gusts of wind or similar events, aremanaged by the circuit board as normal re-ignitions when there is mainsvoltage.

In the case of repeated failed ignitions, said board is moved into a“lockout” state. In these situations, although the function of safeturning off in the presence of inflammable vapours is not activatedbecause there is not a flame, no dangerous conditions arise since thespark of the igniter can ignite the inflammable vapours that may bepresent, and also a reduced amount of time between the first failedignition attempt and “lockout” state is selected, for example less thana few minutes, preferably less than three minutes. It should be notedthat reignition following a “lockout” state requires the presence of theuser (ON button).

It should be noted that the pilot flame in the apparatus according tothe invention is not used to heat any thermoelectric generators and hasthe sole function of igniting the main burner. Therefore, the pilotburner can be designed to generate a smaller amount of energy.Therefore, less energy will be dissipated during the rest (“standby”)periods where the pilot burner remains ignited anyway.

If a thermal safety device 12 intervenes (arranged in series with theflow of air that enters the combustion chamber), the circuit board ofthe control unit does not “directly” notice a possible intervention bythe device 12. Therefore, the system is moved to a “lockout” state sinceit is no longer able to switch on.

Instead, in the event that a thermal safety device comprising amechanical thermostat 14 intervenes, the circuit board of the controlunit is intended for receiving the signal relating to the state of thethermostat and can respond depending on the logic implemented (forexample activating the switch-off of both burners).

The invention therefore meets the predefined objects, thus achieving theadvantages mentioned above with respect to the known solutions.

The advantages achieved by means of the apparatus formed according tothe invention include the fact that the use of a continuous pilot burnerensures that inflammable vapours that may be present near the apparatusare burnt by the pilot flame during the standby periods, thus reducingthe risk of explosion and also allowing for the use of thermal safetydevices that are inexpensive and have an adequate degree of robustnessand reliability. Due to the provision of a buffer battery that isoperatively connected at least to the control unit (and the pilot andmain valves are also commanded to open/close by means of the controlunit as a result), the apparatus is not affected by the problemsassociated with temporary blackouts of the mains, thereby preventing theuser from being left without hot water during the temporary absence of asupply of power from the mains and having to switch the apparatus backon by hand.

Furthermore, the provision of electrically operated main and pilotvalves makes the ignition process more “user friendly” for the user, andalso allows for automatic reignition if the pilot burner has beenaccidentally extinguished. Furthermore, the combination of the featuresmentioned above in the apparatus according to the invention means that athermoelectric generator (thermocouple/thermopile), which is known to besubjected to ageing and loss of performance, does not need to be used.

1. Combustible gas heating apparatus, for heating water, comprising: amain burner (2) arranged in a combustion chamber (3) of the apparatus, apilot burner (4) suitable for generating a pilot flame for igniting themain burner (2), a valve group (5) comprising a main valve (6) arrangedon a main duct (7) for supplying the combustible gas to the main burner(2), and a pilot valve (8) arranged on said main duct (7), upstream ofsaid main valve (6), for supplying gas to the pilot burner (4), a pilotduct (9) branching off from a portion (7 a) of the main duct (7) betweensaid pilot and main valves (8, 6) in order to feed the gas to the pilotburner (4), a system for controlling the supply of gas to said burners,including an electronic control unit (10) that is operatively associatedwith said main and pilot valves (6, 8), a thermal safety device (12)which can be activated in the presence of inflammable vapours in thevicinity of the apparatus and configured to safely extinguish the mainburner (2) when a predetermined temperature threshold in the combustionchamber (3) has been exceeded, said pilot burner (4) configured as acontinuous pilot burner having a permanent flame, the pilot valve (8)and the main valve (6) being electrically-operated valves, an auxiliarybuffer battery (18) being intended to power said electronic control unit(10) if there is a temporary absence of a mains power supply, such thatat least said pilot valve (8) is powered and operated, by means of saidcontrol unit (10), in order to ensure that the pilot flame in the pilotburner (4) is maintained during the absence of a mains power supply. 2.The heating apparatus according to claim 1, wherein said control unit(10) is designed to supply power to, and also operate, the main valve(6) during a temporary absence of a mains power supply, after thecontrol unit (10) has been supplied with power by said auxiliary bufferbattery (18).
 3. The heating apparatus according to claim 1, whereinsaid thermal safety device (12) comprises an interception element (13)designed to selectively intercept the flow of air that is suitable forigniting the flame in the main burner (2) if the temperature detected inthe combustion chamber (3) exceeds the predetermined temperaturethreshold, thus safely extinguishing the main burner (2).
 4. The heatingapparatus according to claim 1, wherein said thermal safety device (12)comprises a mechanical thermostat (14) that can change state if thetemperature in the combustion chamber (3) exceeds the predeterminedtemperature threshold, said control unit (10) being designed torecognize when said mechanical thermostat (14) has changed state inorder to intervene in the form of a command to safely extinguish themain burner (2).
 5. The heating apparatus according to claim 1, whereinsaid control unit (10) is supplied with power from the mains supply andis designed to send electric command signals to the pilot and mainvalves (8, 6) in order to open/close the passage of gas through saidvalves.
 6. The heating apparatus according to claim 1, wherein saidcontrol unit (10) is operatively associated with a first ON button (10),by means of which said unit (10) is activated, determining the start ofthe procedure for igniting the pilot burner (4), an OFF button (20), bymeans of which the user can interrupt the power supply to the controlunit (10) and subsequently command the pilot and main valves to close,and a dial (21) for regulating the temperature, by means of which theuser can set the desired temperature and subsequently ignite the mainburner (2) or not.
 7. The heating apparatus according to claim 1,further comprising a device (15) for damping down the flame, whichcomprises a fireproof grid.
 8. The heating apparatus according to claim1, further comprising a water tank (13 c) intended to be heated by saidapparatus, and a water temperature sensor (13 d) in an electronic waterthermostat, which is designed to compare the water temperature set bythe user with the actual temperature detected by the sensor (13 d).